RKM code

The RKM code,[1] also referred to as "letter and digit code for resistance and capacitance values and tolerances" or "R notation", is a notation to specify resistor and capacitor values defined in the international standard IEC 60062 (formerly IEC 62) since 1952. It is also adopted by various other standards including DIN 40825 (1973), BS 1852 (1974), IS 8186 (1976) and EN 60062 (1993). The significantly updated IEC 60062:2016 comprises the most recent release of the standard.[1]


Originally meant also as part marking code, this shorthand notation is widely used in electrical engineering to denote the values of resistors and capacitors in circuit diagrams and in the production of electronic circuits (for example in bills of material and in silk screens). This method avoids overlooking the decimal separator, which may not be rendered reliably on components or when duplicating documents.

The standards also define a color code for fixed resistors.

Part value code

Examples of resistance values
R47 0.47 ohm
4R7 4.7 ohm
470R 470 ohm
4K7 4.7 kiloohm
47K 47 kiloohm
47K3 47.3 kiloohm
470K 470 kiloohm
4M7 4.7 megaohm

For brevity, the notation omits to always specify the unit (ohm or farad) explicitly and instead relies on implicit knowledge raised from the usage of specific letters either only for resistors or for capacitors,[nb 1] the case used (uppercase letters are typically used for resistors, lowercase letters for capacitors),[nb 2] a part's appearance, and the context.

The notation also avoids using a decimal separator and replaces it by a letter associated with the prefix symbol for the particular value.

This is not only for brevity (for example when printed on the part or PCB), but also to circumvent the problem that decimal separators tend to "disappear" when photocopying printed circuit diagrams.

The code letters are loosely related to the corresponding SI prefix, but there are several exceptions, where the capitalization differs or alternative letters are used.

For example, 8K2 indicates a resistor value of 8.2 kΩ. Additional zeros imply tighter tolerance, for example 15M0.

When the value can be expressed without the need for a prefix, an "R" is used instead of the decimal separator. For example, 1R2 indicates 1.2 Ω, and 18R indicates 18 Ω.

Code letter Prefix Multiplier
Resistance [Ω] Capacitance [F] Name Symbol (SI) Base 10 Base 1000 Value
- p (P[nb 2]) pico- p ×10−12 ×1000−4 ×0.000000000001
- n (N[nb 2]) nano- n ×10−9 ×1000−3 ×0.000000001
- µ (u, U[nb 2]) micro- µ ×10−6 ×1000−2 ×0.000001
L m (M[nb 1][nb 2]) milli- m ×10−3 ×1000−1 ×0.001
R (E[nb 3]) F - - ×100 ×10000 ×1
K (k[nb 4]) - kilo- k ×103 ×10001 ×1000
M[nb 1] - mega- M ×106 ×10002 ×1000000
G - giga- G ×109 ×10003 ×1000000000
T - tera- T ×1012 ×10004 ×1000000000000

For resistances, the standard dictates the use of the uppercase letters L (for 10−3), R (for 100 = 1), K (for 103), M (for 106), and G (for 109) to be used instead of the decimal point.

The usage of the letter R instead of the SI unit symbol Ω for ohms stems from the fact that the Greek letter Ω wasn't (and still isn't) part of most character sets and therefore is sometimes impossible to reproduce, in particular in some CAD/CAM environments. The letter R was chosen because visually it loosely resembles the Ω glyph, and also because it works nicely as a mnemonic for resistance in many languages.

The letters G and T weren't part of the first issue of the standard, which pre-dates the introduction of the SI system (hence the name "RKM code"), but were added after the adoption of the corresponding SI prefixes.

The introduction of the letter L in more recent issues of the standard (instead of an SI prefix m for milli) is justified to maintain the rule of only using uppercase letters for resistances (the otherwise resulting M was already in use for mega).

Similar, the standard prescribes the following lowercase letters for capacitances to be used instead of the decimal point: p (for 10−12), n (for 10−9), µ (for 10−6), m (for 10−3), but uppercase F (for 100 = 1) for farad.

The letters p and n weren't part of the first issue of the standard, but were added after the adoption of the corresponding SI prefixes.

In cases where the Greek letter µ is not available, the standard allows it to be replaced by u (or U, when only uppercase letters are available). This usage of u instead of µ is also in line with ISO 2955 (1974,[2] 1983[3]), DIN 66030 (Vornorm 1973;[4] 1980,[5][6] 2002[7]) and BS 6430 (1983), which allow the prefix μ to be substituted by the letter u (or U) in circumstances in which only the Latin alphabet is available.

Tolerance code

Letter code for resistance and capacitance tolerances:

Code letter Tolerance
Resistance Capacitance Relative Absolute
Symmetrical Asymmetrical C <10 pF only
A A variable (±0.05%) variable variable
B B ±0.1% N/A
C C ±0.25% N/A ±0.25 pF
D D ±0.5% N/A ±0.5 pF
E ±0.005% N/A N/A
F F ±1.0% N/A ±1.0 pF
G G ±2.0% N/A ±2.0 pF
H H ±3.0% N/A N/A
J J ±5.0% N/A N/A
K K ±10% N/A N/A
L ±0.01% N/A N/A
M M ±20% N/A N/A
N ±30% N/A N/A
P ±0.02% N/A N/A
Q N/A −10/+30% N/A
S N/A −20/+50% N/A
T N/A −10/+50% N/A
W ±0.05% N/A N/A
Z N/A −20/+80% N/A

Temperature coefficient code

Letter codes for resistor temperature coefficients:

Code letter ppm/K
K 1
M 5
P 15
Q 25
R 50
S 100
U 250
Z other

Production date code

  • Second character: Month of production
    • 1 to 9 = January to September
    • O = October
    • N = November
    • D = December

Example: V8 = August 2007 (or August 1987)

Corresponding standards

  • IEC 62:1952 (aka IEC 60062:1952), first edition, 1952-01-01
  • IEC 62:1968 (aka IEC 60062:1968), second edition, 1968-01-01
  • IEC 62:1968/AMD1:1968 (aka IEC 60062:1968/AMD1:1968), amended second edition, 1968-12-31
  • IEC 62:1974 (aka IEC 60062:1974)[11]
  • IEC 62:1974/AMD1:1988 (aka IEC 60062:1974/AMD1:1988), amended third edition, 1988-04-30
  • IEC 62:1974/AMD2:1989 (aka IEC 60062:1974/AMD2:1989), amended third edition, 1989-01-01
  • IEC 62:1992 (aka IEC 60062:1992), fourth edition, 1992-03-15
  • IEC 62:1992/AMD1:1995 (aka IEC 60062:1992/AMD1:1995), amended fourth edition, 1995-06-19
  • IEC 60062:2004 (fifth edition, 2004-11-08)[12]
  • IEC 60062:2016 (sixth edition, 2016-07-12)[1]
  • IEC 60062:2016/COR1:2016 (corrected sixth edition, 2016-12-05)
  • EN 60062:1993
  • EN 60062:1994 (1994-10)
  • EN 60062:2005
  • EN 60062:2016
  • BS 1852:1975[13] (related to IEC 60062:1974)
  • BS EN 60062:1994[14]
  • BS EN 60062:2005[15]
  • BS EN 60062:2016[16]
  • DIN 40825:1973-04 (capacitor/resistor value code), DIN 41314:1975-12 (date code)
  • DIN IEC 62:1985-12 (aka DIN IEC 60062:1985-12)
  • DIN IEC 62:1989-10 (aka DIN IEC 60062:1989-10)
  • DIN IEC 62:1990-11 (aka DIN IEC 60062:1990-11)
  • DIN IEC 62:1993-03 (aka DIN IEC 60062:1993-03)
  • DIN EN 60062:1997-09
  • DIN EN 60062:2001-11
  • DIN EN 60062:2005-11
  • ČSN EN 60062
  • DS/EN 60062
  • EVS-EN 60062
  • (GOST) ГОСТ IEC 60062-2014[10] (related to IEC 60062-2004)
  • ILNAS-EN 60062
  • I.S. EN 60062
  • NEN EN IEC 60062
  • NF EN 60062
  • ÖVE/ÖNORM EN 60062
  • PN-EN 60062
  • prМКС EN 60062
  • SN EN 60062
  • TS 2932 EN 60062
  • UNE-EN 60062
  • BIS IS 4114-1967[17]
  • IS 8186-1976[18] (related to IEC 62:1974)
  • JIS C 5062

See also


  1. ^ a b c The letter M was an exception to the rule that all different letters are supposed to be used for resistances and capacitances. Today, a lowercase letter m should be used for capacitances whenever possible to avoid confusion.
  2. ^ a b c d e In old issues of the IEC 60062 standard, uppercase Latin letters were not only used for resistances, but also for capacitance values, whereas newer issues specifically use lowercase letters for capacitors (except for the special case of F).
  3. ^ The usage of the Latin letter E instead of R is not standardized in IEC 60062, but nevertheless sometimes seen in practice. It stems from the fact, that R is used in symbolic names for resistors as well, and it is also used in a similar fashion but with incompatible meaning in other part marking codes. It may therefore cause confusion in some contexts. Visually, the letter E loosely resembles a small Greek letter omega (ω) turned sideways. Historically (f.e. in pre-WWII documents), before ohms were denoted using the uppercase Greek omega (Ω), a small omega (ω) was sometimes used for this purpose as well, as in 56ω for 56 Ω. However, the letter E is conflictive with the similar looking but incompatible E notation in engineering, and it may therefore cause considerable confusion as well.
  4. ^ The IEC 60062 standard prescribes the usage of an uppercase Latin letter K only, however, a lowercase k is often seen in schematics and bills of materials probably because the corresponding SI prefix is defined as a lowercase k.


  1. ^ a b c "IEC 60062:2016-07" (6 ed.). July 2016. Archived from the original on 2018-07-23. Retrieved 2018-07-23. [1]
  2. ^ ISO 2955-1974: lnformation processing - Representations of SI and other units for use in systems with limited character sets (1 ed.). 1974.
  3. ^ "Table 2". ISO 2955-1983: lnformation processing - Representations of SI and other units for use in systems with limited character sets (PDF) (2 ed.). 1983-05-15. Retrieved 2016-12-14. [2]
  4. ^ Vornorm DIN 66030 [Preliminary standard DIN 66030] (in German). January 1973.
  5. ^ DIN 66030: Informationsverarbeitung - Darstellungen von Einheitennamen in Systemen mit beschränktem Schriftzeichenvorrat [Information processing; representations for names of units to be used in systems with limited graphic character sets] (in German) (1 ed.). Beuth Verlag. November 1980. Retrieved 2016-12-14.
  6. ^ "Neue Normen für die Informationsverarbeitung". Computerwoche (in German). 1981-01-09. Archived from the original on 2016-12-14. Retrieved 2016-12-14.
  7. ^ DIN 66030:2002-05 - Informationstechnik - Darstellung von Einheitennamen in Systemen mit beschränktem Schriftzeichenvorrat [Information technology - Representation of SI and other units in systems with limited character sets] (in German). Beuth Verlag. May 2002. Retrieved 2016-12-14.
  8. ^ a b c d e f g h i j k l m n o p q "Precision and Power Resistors (ISA)" (PDF). Swansea, MA, USA: Isotek Corporation / Isabellenhütte. Archived (PDF) from the original on 2017-02-07. Retrieved 2017-02-07.
  9. ^ a b c d e f g h i j k l "Production date code marking system according to IEC 60062, clause 5.1 Two-character code (year/month)" (PDF). Iskra Kondenzatorji. 2017. Archived (PDF) from the original on 2017-02-07. Retrieved 2017-02-07. (NB. Date codes for 2016 and 2017 are obviously wrong.)
  10. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ГОСТ IEC 60062-2014 (PDF) (in Russian). GOST (ГОСТ). 2014.
  11. ^ IEC 60062:1974
  12. ^ https://webstore.iec.ch/p-preview/info_iec60062%7Bed5.0%7Den.pdf
  13. ^ BS 1852:1975.
  14. ^ BS EN 60062:1994.
  15. ^ BS EN 60062:2005.
  16. ^ BS EN 60062:2016.
  17. ^ "www.worldstdindex.com". www.worldstdindex.com.
  18. ^ IS : 8186-1976 (PDF). 1977 [1976]. Archived (PDF) from the original on 2016-12-14. Retrieved 2016-12-14.

External links

Bill of materials

A bill of materials or product structure (sometimes bill of material, BOM or associated list) is a list of the raw materials, sub-assemblies, intermediate assemblies, sub-components, parts, and the quantities of each needed to manufacture an end product. A BOM may be used for communication between manufacturing partners or confined to a single manufacturing plant. A bill of materials is often tied to a production order whose issuance may generate reservations for components in the bill of materials that are in stock and requisitions for components that are not in stock.

A BOM can define products as they are designed (engineering bill of materials), as they are ordered (sales bill of materials), as they are built (manufacturing bill of materials), or as they are maintained (service bill of materials). The different types of BOMs depend on the business need and use for which they are intended. In process industries, the BOM is also known as the formula, recipe, or ingredients list. The phrase "bill of material" (or "BOM") is frequently used by engineers as an adjective to refer not to the literal bill, but to the current production configuration of a product, to distinguish it from modified or improved versions under study or in test.

Sometimes the term "pseudo-bill of materials" or "pseudo-BOM" is used to refer to a more flexible or simplified version. Often a place-holder part number is used to represent a group of related (usually standard) parts that have common attributes and are interchangeable in the context of this BOM.In electronics, the BOM represents the list of components used on the printed wiring board or printed circuit board. Once the design of the circuit is completed, the BOM list is passed on to the PCB layout engineer as well as the component engineer who will procure the components required for the design.


Capacitance is the ratio of the change in an electric charge in a system to the corresponding change in its electric potential. There are two closely related notions of capacitance: self capacitance and mutual capacitance. Any object that can be electrically charged exhibits self capacitance. A material with a large self capacitance holds more electric charge at a given voltage than one with low capacitance. The notion of mutual capacitance is particularly important for understanding the operations of the capacitor, one of the three elementary linear electronic components (along with resistors and inductors).

The capacitance is a function only of the geometry of the design (e.g. area of the plates and the distance between them) and the permittivity of the dielectric material between the plates of the capacitor. For many dielectric materials, the permittivity and thus the capacitance, is independent of the potential difference between the conductors and the total charge on them.

The SI unit of capacitance is the farad (symbol: F), named after the English physicist Michael Faraday. A 1 farad capacitor, when charged with 1 coulomb of electrical charge, has a potential difference of 1 volt between its plates. The reciprocal of capacitance is called elastance.


A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser or condensator. The original name is still widely used in many languages, but not commonly in English.

The physical form and construction of practical capacitors vary widely and many capacitor types are in common use. Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, air, and oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy.

When two conductors experience a potential difference, for example, when a capacitor is attached across a battery, an electric field develops across the dielectric, causing a net positive charge to collect on one plate and net negative charge to collect on the other plate. No current actually flows through the dielectric. However, there is a flow of charge through the source circuit. If the condition is maintained sufficiently long, the current through the source circuit ceases. If a time-varying voltage is applied across the leads of the capacitor, the source experiences an ongoing current due to the charging and discharging cycles of the capacitor.

Capacitance is defined as the ratio of the electric charge on each conductor to the potential difference between them. The unit of capacitance in the International System of Units (SI) is the farad (F), defined as one coulomb per volt (1 C/V). Capacitance values of typical capacitors for use in general electronics range from about 1 picofarad (pF) (10−12 F) to about 1 millifarad (mF) (10−3 F).

The capacitance of a capacitor is proportional to the surface area of the plates (conductors) and inversely related to the gap between them. In practice, the dielectric between the plates passes a small amount of leakage current. It has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance.

Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits they tune radios to particular frequencies. In electric power transmission systems, they stabilize voltage and power flow. The property of energy storage in capacitors was exploited as dynamic memory in early digital computers.


The cifrão (Portuguese pronunciation: [siˈfɾɐ̃w̃] (listen)) is a currency sign similar to the dollar sign ($) but always written with two vertical lines: . It is the symbol of the former Portuguese currency and other past Brazilian currencies such as the Brazilian real (sign: R$; ISO: BRL) and is the official sign of the Cape Verdean escudo (ISO 4217: CVE).

It was formerly used by the Portuguese escudo (ISO: PTE) before its replacement by the euro and by the Portuguese Timor escudo (ISO: TPE) before its replacement by the Indonesian rupiah and the US dollar. In Portuguese and Cape Verdean usage, the cifrão is placed as a decimal point between the escudo and centavo values (e.g., 2$50). The name originates in the Arabic cifr.

Electrical resistance and conductance

The electrical resistance of an object is a measure of its opposition to the flow of electric current. The inverse quantity is electrical conductance, and is the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the notion of mechanical friction. The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S).

The resistance of an object depends in large part on the material it is made of—objects made of electrical insulators like rubber tend to have very high resistance and low conductivity, while objects made of electrical conductors like metals tend to have very low resistance and high conductivity. This material dependence is quantified by resistivity or conductivity. However, resistance and conductance are extensive rather than bulk properties, meaning that they also depend on the size and shape of an object. For example, a wire's resistance is higher if it is long and thin, and lower if it is short and thick. All objects show some resistance, except for superconductors, which have a resistance of zero.

The resistance (R) of an object is defined as the ratio of voltage across it (V) to current through it (I), while the conductance (G) is the inverse:

For a wide variety of materials and conditions, V and I are directly proportional to each other, and therefore R and G are constants (although they will depend on the size and shape of the object, the material it is made of, and other factors like temperature or strain). This proportionality is called Ohm's law, and materials that satisfy it are called ohmic materials.

In other cases, such as a transformer, diode or battery, V and I are not directly proportional. The ratio V/I is sometimes still useful, and is referred to as a "chordal resistance" or "static resistance", since it corresponds to the inverse slope of a chord between the origin and an I–V curve. In other situations, the derivative may be most useful; this is called the "differential resistance".

Engineering notation

Engineering notation or engineering form is a version of scientific notation in which the exponent of ten must be divisible by three (i.e., they are powers of a thousand, but written as, for example, 106 instead of 10002). As an alternative to writing powers of 10, SI prefixes can be used, which also usually provide steps of a factor of a thousand.On most calculators, engineering notation is called "ENG" mode.


Giga ( or ) is a unit prefix in the metric system denoting a factor of a (short-form) billion (109 or 1000000000). It has the symbol G.

Giga is derived from the Greek word γίγας, meaning "giant". The Oxford English Dictionary reports the earliest written use of giga in this sense to be in the Reports of the IUPAC 14th Conference in 1947: "The following prefixes to abbreviations for the names of units should be used: G giga 109×".When referring to information units in computing, such as gigabyte, giga may sometimes mean 1073741824 (230), although such use is inconsistent, contrary to standards and has been discouraged by the standards organizations. The inconsistency is that gigabit is never (or very rarely) used with the binary interpretation of the prefix, while gigabyte is sometimes used this way. The binary prefix gibi has been adopted for 230, while reserving giga exclusively for the metric definition.


Kilo is a decimal unit prefix in the metric system denoting multiplication by one thousand (103). It is used in the International System of Units where it has the unit symbol k, in lower case.

The prefix kilo is derived from the Greek word χίλιοι (chilioi), meaning "thousand". It was originally adopted by Antoine Lavoisier's research group in 1795, and introduced into the metric system in France with its establishment in 1799.

In 19th century English it was sometimes spelled chilio, in line with a puristic opinion by Thomas Young


Legibility is the ease with which a reader can recognize individual characters in text. "The legibility of a typeface is related to the characteristics inherent in its design … which relate to the ability to distinguish one letter from the other." Aspects of type design that affect legibility include "x-height, character shapes, stroke contrast, the size of its counters, serifs or lack thereof, and weight."Legibility is different from readability. Readability is the ease with which a reader can recognize words, sentences, and paragraphs. Legibility is a component of readability. Other typographic factors that affect readability include font choice, point size, kerning, tracking, line length, leading, and justification.


Mega is a unit prefix in metric systems of units denoting a factor of one million (106 or 1000000). It has the unit symbol M. It was confirmed for use in the International System of Units (SI) in 1960. Mega comes from Ancient Greek: μέγας, translit. megas, lit. 'great'.

Metric prefix

A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. While all metric prefixes in common use today are decadic, historically there have been a number of binary metric prefixes as well. Each prefix has a unique symbol that is prepended to the unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand: one kilogram is equal to one thousand grams. The prefix milli-, likewise, may be added to metre to indicate division by one thousand; one millimetre is equal to one thousandth of a metre.

Decimal multiplicative prefixes have been a feature of all forms of the metric system, with six of these dating back to the system's introduction in the 1790s. Metric prefixes have also been used with some non-metric units. The SI prefixes are standardized for use in the International System of Units (SI) by the International Bureau of Weights and Measures (BIPM) in resolutions dating from 1960 to 1991. Since 2009, they have formed part of the International System of Quantities.


Micro- (Greek letter μ or legacy micro symbol µ) is a unit prefix in the metric system denoting a factor of 10−6 (one millionth). Confirmed in 1960, the prefix comes from the Greek μικρός (mikrós), meaning "small".

The symbol for the prefix comes from the Greek letter μ (mu). It is the only SI prefix which uses a character not from the Latin alphabet. "mc" is commonly used as a prefix when the character "μ" is not available; for example, "mcg" commonly denotes a microgram. Also the letter u instead of μ is allowed by one of the ISO documents.


Typical bacteria are 1 to 10 micrometres in diameter.

Eukaryotic cells are typically 10 to 100 micrometres in diameter.


Milli- (symbol m) is a unit prefix in the metric system denoting a factor of one thousandth (10−3). Proposed in 1793 and adopted in 1795, the prefix comes from the Latin mille, meaning "one thousand" (the Latin plural is milia). Since 1960, the prefix is part of the International System of Units (SI).


Nano- (symbol n) is a unit prefix meaning "one billionth". Used primarily with the metric system, this prefix denotes a factor of 10−9 or 0.000000001. It is frequently encountered in science and electronics for prefixing units of time and length.


One nanometer is about the length that a fingernail grows in one second.

Three gold atoms lined up are about one nanometer long.

If a toy marble were scaled down to one nanometer wide, Earth would scale to about one meter (3.3 feet) wide.

One nanosecond is about the time required for light to travel 30 cm in air, or 20 cm in an optical fiber.The prefix derives from the Greek νᾶνος (Latin nanus), meaning "dwarf". The General Conference on Weights and Measures (CGPM) officially endorsed the usage of nano as a standard prefix in 1960.

When used as a prefix for something other than a unit of measure (as for example in words like "nanoscience"), nano refers to nanotechnology, or means "on a scale of nanometres". See nanoscopic scale.


Pico- (symbol p) is a unit prefix in the metric system denoting one trillionth, a factor of 10−12 (0.000000000001).

Derived from the Spanish pico, meaning peak, beak, bit, this was one of the original 12 prefixes defined in 1960 when the International System of Units was established.The radius of atoms range from 25 picometers (hydrogen) to 260 picometers (caesium). One picolight-year is about nine kilometers (six miles).


RKM or rkm can refer to:

R.K.M & Ken-Y, a Grammy Award-nominated reggaeton duo

rkm, River kilometer

the ISO 639-3 code for the Marka language

ROM Kernel Manual of the Amiga ROM

Rotary Piston Machine (German Rotationskolbenmaschine)

Rybnicki Klub Motorowy (Rybnik's Motorcycle Club)

RKM code, a letter and digit code for resistor values

Ramakrishna Mission, Hindu religious and spiritual organization


A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat, may be used as part of motor controls, in power distribution systems, or as test loads for generators.

Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity.

Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds and forms. Resistors are also implemented within integrated circuits.

The electrical function of a resistor is specified by its resistance: common commercial resistors are manufactured over a range of more than nine orders of magnitude. The nominal value of the resistance falls within the manufacturing tolerance, indicated on the component.

Scientific notation

Scientific notation (also referred to as scientific form or standard index form, or standard form in the UK) is a way of expressing numbers that are too big or too small to be conveniently written in decimal form. It is commonly used by scientists, mathematicians and engineers, in part because it can simplify certain arithmetic operations. On scientific calculators it is usually known as "SCI" display mode.

In scientific notation all numbers are written in the form

m × 10n(m times ten raised to the power of n), where the exponent n is an integer, and the coefficient m is any real number. The integer n is called the

order of magnitude and the real number m is called the significand or mantissa. However, the term "mantissa" may cause confusion because it is the name of the fractional part of the common logarithm. If the number is negative then a minus sign precedes m (as in ordinary decimal notation). In normalized notation, the exponent is chosen so that the absolute value of the coefficient is at least one but less than ten.

Decimal floating point is a computer arithmetic system closely related to scientific notation.


Tera is a unit prefix in the metric system denoting multiplication by 1012 or 1000000000000 (one trillion short scale; one billion long scale). It has the symbol T. Tera is derived from Greek word τέρας teras, meaning "monster". The unit prefix was confirmed for use in the International System of Units (SI) in 1960.

Examples of its use:

terahertz radiation: electromagnetic waves within the band of frequencies from 0.3 to 3 THz. Visible light is around 500 THz.

terabit and terabyte, units used in data storage.

teragram: equal to 109 kg. The Great Pyramid of Giza has a mass of about 6 Tg.

terasecond: approximately 31,558 years

teralitre: equal to 109 m3. Lake Zurich contains about 4 TL of water.

terawatt: used to measure total human energy consumption. In 2010 it was 16 TW (TJ/s).

terametre (= 1,000,000,000 km): Light travels 1.079 Tm in one hour.

IEC standards
ISO/IEC standards

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